The Influence of Cooling Rate on the Microstructure and Microsegregation in Al–30Sn Binary Alloy

Aluminum–tin alloys have wide industrial uses, especially in tribological applications. Their structure is consisted of Al-α dendrites (bearing the mechanical load) surrounded by Sn-rich interdendritic layers that function as a solid lubricant. Despite extensive research on solidification behavior of Al–Sn and Al–Sn-based alloys, microsegregation is not yet fully understood. The aim of this article is to study the effect of cooling rate on the microsegregation of Al–30 wt% Sn. Three cooling rates including 3.5, 12.3, and 95.8 K/s were achieved by using three various molds made of sand, brass, and water-cooled brass with the same respective die hole geometries. The results showed that the microstructure becomes much finer with increasing cooling rate. The minimum concentration of Sn in Al was increased by increasing cooling rate approximately four times of equilibrium concentration. The hardness increased mainly as a result of microstructure refinement.